System And Method For Wireless Drilling And Non-Rotating Mining Extenders In A Drilling Operation

ABSTRACT

Various embodiments of methods and systems for wireless power and data communications transmissions to a sensor subassembly below a mud motor in a bottom hole assembly are disclosed. Power and/or communications are transmitted through stationary or fixed coils. By leveraging resonantly tuned circuits and impedance matching techniques for the stationary coils, power and/or communications can be transmitted efficiently from one stationary coil to the other stationary coil despite any vibration and/or misalignment of the two coils.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 61/704,820, entitled “System And Method ForWireless Drilling And Mining Extenders In A Drilling Operation, andfiled on Sep. 24, 2012, U.S. Provisional Patent Application Ser. No.61/704,805, entitled “System And Method for Wireless Power And DataTransmission In A Mud Motor,” and filed on Sep. 24, 2012, and U.S.Provisional Patent Application Ser. No. 61/704,758, entitled “PositiveDisplacement Motor Rotary Steerable System And Apparatus,” and filed onSep. 24, 2012, the disclosures of which are hereby incorporated byreference in their entireties.

DESCRIPTION OF THE RELATED ART

Bottom hole assemblies (“BHA”) at the end of a typical drill string usedin the drilling and mining industry today may be a complex assembly oftechnology that includes not only a drill bit, but also an array ofserially connected drill string components or tools. The various drillstring tools that make up a BHA commonly include electrically poweredsystems on a chip (“SoC”) designed to leverage local sensors for thecollection, processing and transmission of data that can be used tooptimize a drilling strategy. In many cases, the various tools that makeup a BHA are in bidirectional communication.

As one might expect, a BHA may be an equipment assembly with a hardeneddesign that can withstand the demands of a drill string. Failure of aBHA, whether mechanically or electrically, inevitably brings aboutexpensive and unwelcomed operating costs as the drilling process may behalted and the drill string retracted from the bore so that the failedBHA can be repaired. In many cases, retraction of a drill string torepair a failed BHA can range in cost from hundreds of thousands ofdollars to millions of dollars.

A common failure point for BHAs is the point of connection from tool totool, which is naturally prone to failure from adverse fluid ingressand/or misalignment between adjacent tools. While the individual toolsmay be robust in design, the mechanical and electrical connectionsbetween the tools may be a natural “weak point” that often determinesthe overall reliability of the BHA system.

SUMMARY OF THE DISCLOSURE

Various embodiments of methods and systems for wireless power and datacommunications transmissions in a BHA are disclosed. The efficienttransfer of electrical power and/or communication signals between twootherwise weakly, stationary coupled coils in a BHA may be accomplishedin various embodiments that may leverage resonantly tuned circuits andimpedance matching techniques. In this way, a wireless coupling may beprovided between two fixed or stationary tools so that a directmechanical connection for power and/or communications is not requiredwhen assembling the tools together and while they are operated in a borehole. A gap between the tuned coils may exist and does not degradeperformance of power and communications transfer between the coil. Tocompensate for any potential flux leakage, embodiments resonateinductively coupled primary and secondary coils at the same frequency.Further, in some embodiments, the source resistance is matched to thetransmitting coil impedance and the load resistance is matched to thereceiving coil impedance.

Power and/or communications may be transmitted through a stationaryannular coil to an inductively coupled stationary second, mandrel coil(it is envisioned that various embodiments may employ any combination ofannular and mandrel coils). By using resonantly tuned circuits andimpedance matching techniques for the stationary coils, power and/orcommunications may be transmitted efficiently from one stationary coilto the other despite relative movement/vibration and misalignment of thetwo stationary coils. For example, to compensate for flux leakage,embodiments resonate inductively coupled primary and secondary coils atthe same frequency.

Additionally, in some embodiments, the source resistance is matched tothe transmitting coil impedance and the load resistance is matched tothe receiving coil impedance.

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Figures, like reference numerals refer to like parts throughoutthe various views unless otherwise indicated. For reference numeralswith letter character designations such as “102A” or “102B”, the lettercharacter designations may differentiate two like parts or elementspresent in the same figure. Letter character designations for referencenumerals may be omitted when it is intended that a reference numeral toencompass parts having the same reference numeral in figures.

FIG. 1A is a diagram of a system for wireless drilling and miningextenders in a drilling operation;

FIG. 1B is a diagram of a wellsite drilling system that forms part ofthe system illustrated in FIG. 1A;

FIG. 2 is a schematic drawing depicting a primary or transmittingcircuit and a secondary or receiving circuit;

FIG. 3 is a schematic drawing depicting a primary or transmittingcircuit and a secondary or receiving circuit with transformers havingturn ratios N_(S):1 and N_(L):1 that may used to match impedances;

FIG. 4 is a schematic drawing depicting an alternative circuit to thatwhich is depicted in FIG. 3 and having parallel capacitors that are usedto resonate the coils' self-inductances;

FIGS. 5A-5B illustrate an embodiment of a receiving coil inside atransmitting coil;

FIGS. 6-7 are graphs illustrating the variation in k versus axialdisplacement of the receiving coil when x=0 is small and the transversedisplacement when z=0 produces very small changes in k of givenembodiments, respectively;

FIGS. 8-9 are graphs illustrating that power efficiency may also becalculated for displacements from the center in the z direction and inthe x direction, respectively, of given embodiments;

FIG. 10 is a graph illustrating that the sensitivity of the powerefficiency to frequency drifts may be relatively small in someembodiments;

FIG. 11 is a graph illustrating that drifts in the components values ofsome embodiments do not have a large effect on the power efficiency ofthe embodiment;

FIG. 12 depicts a particular embodiment configured to convert input DCpower to a high frequency AC signal, f₀, via a DC/AC convertor;

FIG. 13 depicts a particular embodiment configured to pass AC powerthrough the coils;

FIG. 14 depicts a particular embodiment that includes additionalsecondary coils configured to transmit and receive data;

FIGS. 15A1-15C2 are diagrams of tools in a bottom hole assembly of adrill string that are coupled via embodiments of a wireless drilling andmining extender;

FIG. 16A illustrates a wireless power distribution scheme betweenstationary tools that leverages alternating current (“AC”) to transmitpower across various tools in a BHA that includes wireless drilling andmining extenders; and

FIG. 16B illustrates wireless power distribution scheme betweenstationary tools that leverages alternating current (“AC”) and directcurrent (“DC”) to transmit power across various tools in a BHA thatincludes wireless drilling and mining extenders.

DETAILED DESCRIPTION

The system described below mentions how power and/or communications mayflow from one drill collar to another. The inventive system may transmitpower and/or communications in either direction and/or in bothdirections as understood by one of ordinary skill in the art.

Referring initially to FIG. 1A, this figure is a diagram of a system 102for controlling and monitoring a drilling operation. The system 102includes a control module 101 that is part of a controller 106. Thesystem 102 also includes a drilling system 104, which has a logging andcontrol module 95, a bottom hole assembly (“BHA”) 100, and wirelesspower and data connections 402. The wireless power and data connections402 may exist between several elements of the BHA as will be explainedbelow.

The controller 106 further includes a display 147 for conveying alerts110A and status information 115A that are produced by an alerts module110B and a status module 115B. The controller 106 in some instances maycommunicate directly with the drilling system 104 as indicated by dashedline 99 or the controller 106 may communicate indirectly with thedrilling system 104 using the communications network 142

The controller 106 and the drilling system 104 may be coupled to thecommunications network 142 via communication links 103. Many of thesystem elements illustrated in FIG. 1A are coupled via communicationslinks 103 to the communications network 142.

FIG. 1B illustrates a wellsite drilling system 104 that forms part ofthe system 102 illustrated in FIG. 1A. The wellsite can be onshore oroffshore. In this system 104, a borehole 11 is formed in subsurfaceformations by rotary drilling in a manner that is known to one ofordinary skill in the art. Embodiments of the system 104 can also usedirectional drilling, as will be described hereinafter. The drillingsystem 104 includes the logging and control module 95 as discussed abovein connection with FIG. 1A.

A drill string 12 is suspended within the borehole 11 and has a bottomhole assembly (“BHA”) 100 which includes a drill bit 105 at its lowerend. The surface system includes platform and derrick assembly 10positioned over the borehole 11, the assembly 10 including a rotarytable 16, kelly 17, hook 18 and rotary swivel 19. The drill string 12 isrotated by the rotary table 16, energized by means not shown, whichengages the kelly 17 at the upper end of the drill string. The drillstring 12 is suspended from a hook 18, attached to a traveling block(also not shown), through the kelly 17 and a rotary swivel 19 whichpermits rotation of the drill string 12 relative to the hook 18. As isknown to one of ordinary skill in the art, a top drive system couldalternatively be used instead of the kelly 17 and rotary table 16 torotate the drill string 12 from the surface. The drill string 12 may beassembled from a plurality of segments 125 of pipe and/or collarsthreadedly joined end to end.

In the embodiment of FIG. 1B, the surface system further includesdrilling fluid or mud 26 stored in a pit 27 formed at the well site. Apump 29 delivers the drilling fluid 26 to the interior of the drillstring 12 via a port in the swivel 19, causing the drilling fluid toflow downwardly through the drill string 12 as indicated by thedirectional arrow 8. The drilling fluid exits the drill string 12 viaports in the drill bit 105, and then circulates upwardly through theannulus region between the outside of the drill string 12 and the wallof the borehole 11, as indicated by the directional arrows 9. In thissystem as understood by one of ordinary skill in the art, the drillingfluid 26 lubricates the drill bit 105 and carries formation cuttings upto the surface as it is returned to the pit 27 for cleaning andrecirculation.

The BHA 100 of the illustrated embodiment may include alogging-while-drilling (“LWD”) module 120, a measuring-while-drilling(“MWD”) module 130, a roto-steerable system (“RSS”) and motor 150 (alsoillustrated as 280 in FIG. 15 described below), and drill bit 105.

The LWD module 120 is housed in a special type of drill collar, as isknown to one of ordinary skill in the art, and can contain one or aplurality of known types of logging tools. It will also be understoodthat more than one LWD 120 and/or MWD module 130 can be employed, e.g.as represented at 120A. (References, throughout, to a module at theposition of 120A can alternatively mean a module at the position of 120Bas well.) The LWD module 120 includes capabilities for measuring,processing, and storing information, as well as for communicating withthe surface equipment. In the present embodiment, the LWD module 120includes a directional resistivity measuring device.

The MWD module 130 is also housed in a special type of drill collar, asis known to one of ordinary skill in the art, and can contain one ormore devices for measuring characteristics of the drill string 12 anddrill bit 105. The MWD module 130 may further include an apparatus (notshown) for generating electrical power to the BHA 100.

This apparatus may include a mud turbine generator powered by the flowof the drilling fluid 26, it being understood by one of ordinary skillin the art that other power and/or battery systems may be employed. Inthe embodiment, the MWD module 130 includes one or more of the followingtypes of measuring devices: a weight-on-bit measuring device, a torquemeasuring device, a vibration measuring device, a shock measuringdevice, a stick slip measuring device, a direction measuring device, andan inclination measuring device.

The foregoing examples of wireline and drill string conveyance of a welllogging instrument are not to be construed as a limitation on the typesof conveyance that may be used for the well logging instrument. Anyother conveyance known to one of ordinary skill in the art may be used,including without limitation, slickline (solid wire cable), coiledtubing, well tractor and production tubing.

FIG. 2 is a schematic drawing depicting a primary or transmittingcircuit 210 and a secondary or receiving circuit 220. In thisdescription, the time dependence is assumed to be exp(jωt) where ω=2πfand f is the frequency in Hertz. Returning to the FIG. 2 illustration,the transmitting coil is represented as an inductance L₁ and thereceiving coil as L₂. In the primary circuit 210, a voltage generatorwith constant output voltage V_(S) and source resistance R_(S) drives acurrent I₁ through a tuning capacitor C₁ and primary coil havingself-inductance L₁ and series resistance R₁. The secondary circuit 220has self-inductance L₂ and series resistance R₂. The resistances, R₁ andR₂, may be due to the coils' wires, to losses in the coils magneticcores (if present), and to conductive materials or mediums surroundingthe coils. The Emf (electromotive force) generated in the receiving coilis V₂, which drives current I₂ through the load resistance R_(L) andtuning capacitor C₂. The mutual inductance between the two coils is M,and the coupling coefficient k is defined as:

k=M/√{square root over (L ₁ L ₂)}  (1)

While a conventional inductive coupler has k≈1, weakly coupled coils mayhave a value for k less than 1 such as, for example, less than or equalto about 0.9. To compensate for weak coupling, the primary and secondarycoils in the various embodiments are resonated at the same frequency.The resonance frequency is calculated as:

$\begin{matrix}{\omega_{0} = {\frac{1}{\sqrt{L_{1}C_{1}}} = \frac{1}{\sqrt{L_{2}C_{2}}}}} & (2)\end{matrix}$

At resonance, the reactance due to L₁ is cancelled by the reactance dueto C₁. Similarly, the reactance due to L₂ is cancelled by the reactancedue to C₂. Efficient power transfer may occur at the resonancefrequency, f₀=ω₀/2π. In addition, both coils may be associated with highquality factors, defined as:

$\begin{matrix}{{Q_{1} = \frac{\omega \; L_{1}}{R_{1}}}{and}{Q_{2} = {\frac{\omega \; L_{2}}{R_{2}}.}}} & (3)\end{matrix}$

The quality factors, Q, may be greater than or equal to about 10 and insome embodiments greater than or equal to about 100. As is understood byone of ordinary skill in the art, the quality factor of a coil is adimensionless parameter that characterizes the coil's bandwidth relativeto its center frequency and, as such, a higher Q value may thus indicatea lower rate of energy loss as compared to coils with lower Q values.

If the coils are loosely coupled such that k<1, then efficient powertransfer may be achieved provided the figure of merit, U, is larger thanone such as, for example, greater than or equal to about 3:

U=k√{square root over (Q ₁ Q ₂)}>>1.  (4)

The primary and secondary circuits are coupled together via:

V ₁ =jωL ₁ I ₁ +jωM I ₂ and V ₂ =jωL ₂ I ₂ +jωM I ₁,  (5)

where V₁ is the voltage across the transmitting coil. Note that thecurrent is defined as clockwise in the primary circuit andcounterclockwise in the secondary circuit. The power delivered to theload resistance is:

P _(L)=½R _(L) |I ₂|²,  (6)

while the maximum theoretical power output from the fixed voltage sourceV_(S) into a load is:

$\begin{matrix}{P_{MAX} = {\frac{{V_{S}}^{2}}{8\; R_{S}}.}} & (7)\end{matrix}$

The power efficiency is defined as the power delivered to the loaddivided by the maximum possible power output from the source,

$\begin{matrix}{\eta \equiv {\frac{P_{L}}{P_{MAX}}.}} & (8)\end{matrix}$

In order to optimize the power efficiency, η, the source resistance maybe matched to the impedance of the rest of the circuitry. Referring toFIG. 2, Z₁ is the impedance looking from the source toward the load andis given by:

$\begin{matrix}{Z_{1} = {R_{1} - {j/\left( {\omega \; C_{1}} \right)} + {j\; \omega \; L_{1}} + \frac{\omega^{2}M^{2}}{R_{2} + R_{L} + {j\; \omega \; L_{2}} - {j/\left( {\omega \; C_{2}} \right)}}}} & (9)\end{matrix}$

When ω=ω₀, Z₁ is purely resistive and may equal R_(S) for maximumefficiency.

$\begin{matrix}{Z_{1} = {{R_{1} + \frac{\omega^{2}M^{2}}{R_{2} + R_{L}}} \equiv {R_{S}.}}} & (10)\end{matrix}$

Similarly, the impedance seen by the load looking back toward the sourceis

$\begin{matrix}{Z_{2} = {R_{2} - {j/\left( {\omega \; C_{2}} \right)} + {j\; \omega \; L_{2}} + \frac{\omega^{2}M^{2}}{R_{1} + R_{S} + {j\; \omega \; L_{1}} - {j/\left( {\omega \; C_{1}} \right)}}}} & (11)\end{matrix}$

When ω=ω₀, Z₂ is purely resistive and R_(L) should equal Z₂ for maximumefficiency

$\begin{matrix}{Z_{2} = {{R_{2} + \frac{\omega^{2}M^{2}}{R_{1} + R_{S}}} \equiv {R_{L}.}}} & (12)\end{matrix}$

The power delivered to the load is then:

$\begin{matrix}{{P_{L} = {\frac{1}{2}\frac{R_{L}\omega_{0}^{2}M^{2}{V_{S}}^{2}}{\left\lbrack {{\left( {R_{S} + R_{1}} \right)\left( {R_{2} + R_{L}} \right)} + {\omega_{0}^{2}M^{2}}} \right\rbrack^{2}}}},} & (13)\end{matrix}$

and the power efficiency is the power delivered to the load divided bythe maximum possible power output,

$\begin{matrix}{{\eta \equiv \frac{P_{L}}{P_{MAX}}} = {\frac{4\; R_{S}R_{L}\omega_{0}^{2}M^{2}}{\left\lbrack {{\left( {R_{S} + R_{1}} \right)\left( {R_{2} + R_{L}} \right)} + {\omega_{0}^{2}M^{2}}} \right\rbrack^{2}}.}} & (14)\end{matrix}$

The optimum values for R_(L) and R_(L) may be obtained by simultaneouslysolving

$\begin{matrix}{{R_{S} = {R_{1} + \frac{\omega^{2}M^{2}}{R_{2} + R_{L}}}}{and}{{R_{L} = {R_{2} + \frac{\omega^{2}M^{2}}{R_{1} + R_{S}}}},}} & (15)\end{matrix}$

with the result that:

R _(S) =R ₁√{square root over (1+k ² Q ₁ Q ₂)} and R _(L) =R ₂√{squareroot over (1+k ² Q ₁ Q ₂)}.  (16)

If the source and load resistances do not satisfy equations (16), thenit is envisioned that standard methods may be used to transform theimpedances. For example, as shown in the FIG. 3 illustration,transformers with turn ratios N_(S):1 and N_(L):1 may be used to matchimpedances as per equations (16). Alternatively, the circuit illustratedin FIG. 4 may be used. In such an embodiment in FIG. 4, parallelcapacitors are used to resonate the coils' self-inductances according toequation (2). As before, Z₁ is defined as the impedance seen by thesource looking toward the load, while Z₂ is defined as the impedanceseen by the load looking toward the source. In addition, there are twomatching impedances, Z_(S) and Z_(T) which may be used to cancel anyreactance that would otherwise be seen by the source or load. Hence Z₁and Z₂ are purely resistive with the proper choices of Z_(S) and Z_(T).Notably, the source resistance R_(S) may equal Z₁, and the loadresistance R_(L) may equal Z₂. The procedures for optimizing efficiencywith series capacitance or with parallel capacitance may be the same,and both approaches may provide high efficiencies.

Turning now to FIGS. 5A and 5B, a cross sectional view of two coils 232,234 is illustrated in FIG. 5A and a side view of the two coils 232, 234is illustrated in FIG. 5B. In these two figures, a receiving coil 232inside a transmitting coil 234 of a particular embodiment 230 isdepicted. The receiving coil 232 includes a ferrite rod core 235 that,in some embodiments, may be about 12.5 mm (about 0.49 inch) in diameterand about 96 mm (about 3.78 inches) long with about thirty-two turns ofwire 237. Notably, although specific dimensions and/or quantities ofvarious components may be offered in this description, it will beunderstood by one of ordinary skill in the art that the embodiments arenot limited to the specific dimensions and/or quantities describedherein.

Returning to FIG. 5, the transmitting coil 234 may include an insulatinghousing 236, about twenty-five turns of wire 239, and an outer shell offerrite 238. The wall thickness of the ferrite shell 238 in the FIG. 5embodiment may be about 1.3 mm (about 0.05 inch). In certainembodiments, the overall size of the transmitting coil 234 may be about90 mm (about 3.54 inch) in diameter by about 150 mm (about 5.90 inches)long. The receiving coil 232 may reside inside the transmitting coil234, which is annular.

The receiving coil 232 may be free to move in the axial (z) direction orin the transverse direction (x) with respect to the transmitting coil234. In addition, the receiving coil 232 may be able to rotate on axiswith respect to the transmitting coil 234. The region between the twocoils 232, 234 may be filled with air, fresh water, salt water, oil,natural gas, drilling fluid (known as “mud”), or any other liquid orgas. The transmitting coil 234 may also be mounted inside a metal tube,with minimal affect on the power efficiency because the magnetic fluxmay be captured by, and returned through, the ferrite shell 238 of thetransmitting coil 234.

The operating frequency for these coils 232, 234 may vary according tothe particular embodiment, but, for the FIG. 5 example 230, a resonantfrequency f=about 100 kHz may be assumed. At this frequency, thetransmitting coil 234 properties are: L₁=6.76·10⁻⁵ Henries and R₁=0.053ohms, and the receiving coil 232 properties are L₂=7.55·10⁻⁵ Henries andR₂=0.040 ohms. The tuning capacitors are C₁=3.75·10⁻⁸ Farads andC₂=3.36·10⁻⁸ Farads. Notably, the coupling coefficient k value dependson the position of the receiving coil 232 inside the transmitting coil234. The receiving coil 232 is centered when x=0 and z=0 and there isk=0.64.

The variation in k versus axial displacement of the receiving coil 232when x=0 may be relatively small, as illustrated by the graph 250 inFIG. 6. The transverse displacement when z=0 may produce very smallchanges ink, as illustrated by the graph 252 in FIG. 7. The receivingcoil 232 may rotate about the z-axis without affecting k because thecoils are azimuthally symmetric. According to equations (16), an optimumvalue for the source resistance may be R_(S)=32 ohms, and for the loadresistance may be R_(L)=24 ohms when the receiving coil 232 is centeredat x=0 and z=0. The power efficiency may thus be η=99.5%.

The power efficiency may also be calculated for displacements from thecenter in the z direction in mm (as illustrated by the graph 254 in FIG.8) and in the x direction in mm (as illustrated by the graph 256 in FIG.9). It is envisioned that the efficiency may be greater than about 99%for axial displacements up to about 20.0 mm (about 0.79 inch) in certainembodiments, and greater than about 95% for axial displacements up toabout 35.0 mm (about 1.38 inches). It is further envisioned that theefficiency may be greater than 98% for transverse displacements up to20.0 mm (about 0.79 inch) in some embodiments. Hence, the position ofthe receiving coil 232 inside the transmitting coil 234 may vary in someembodiments without reducing the ability of the two coils 232, 234 toefficiently transfer power.

Referring now to FIG. 10, it can be seen in the illustrative graph 258where the Y-axis denotes efficiency in percentage and the X-axis denotesfrequency in Hz that the sensitivity of the power efficiency tofrequency drifts may be relatively small. A ±10% variation in frequencymay produce minor effects, while the coil parameters may be held fixed.The power efficiency at 90,000 Hz is better than about 95%, and thepower efficiency at 110,000 Hz is still greater than about 99%.Similarly, drifts in the component values may not have a large effect onthe power efficiency. For example, both tuning capacitors C₁ and C₂ areallowed to increase by about 10% and by about 20% as illustrated in thegraph 260 of FIG. 11. Notably, the other parameters are held fixed,except for the coupling coefficient k. The impact of the powerefficiency is negligible. As such, the system described herein would beunderstood by one of ordinary skill in the art to be robust.

It is also envisioned that power may be transmitted from the inner coilto the outer coil of particular embodiments, interchanging the roles oftransmitter and receiver. It is envisioned that the same powerefficiency would be realized in both cases.

Referring to FIG. 12, an electronic configuration 262 is illustrated forconverting input DC power to a high frequency AC signal, f₀, via a DC/ACconvertor. The transmitter circuit in the configuration 262 excites thetransmitting coil at resonant frequency f₀. The receiving circuit drivesan AC/DC convertor, which provides DC power output for subsequentelectronics. This system 262 is appropriate for efficient passing DCpower across the coils.

Turning to FIG. 13, AC power can be passed through the coils. Input ACpower at frequency f₁ is converted to resonant frequency f₀ by afrequency convertor. Normally this would be a step up convertor withf₀>>f₁. The receiver circuit outputs power at frequency f₀, which isconverted back to AC power at frequency f₁. Alternatively, as one ofordinary skill in the art recognizes, the FIG. 13 embodiment 264 couldbe modified to accept DC power in and produce AC power out, and viceversa.

In lieu of, or in addition to, passing power, data signals may betransferred from one coil to the other in certain embodiments by avariety of means. In the above example, power is transferred using anabout 100.0 kHz oscillating magnetic field. It is envisioned that thisoscillating signal may also be used as a carrier frequency withamplitude modulation, phase modulation, or frequency modulation used totransfer data from the transmitting coil to the receiving coil. Suchwould provide a one-way data transfer.

An alternative embodiment includes additional secondary coils totransmit and receive data in parallel with any power transmissionsoccurring between the other coils described above, as illustrated inFIG. 14. Such an arrangement may provide two-way data communication insome embodiments. The secondary data coils 266, 268 may be associatedwith relatively low power efficiencies of less than about 10%. It isenvisioned that in some embodiments the data transfer may beaccomplished with a good signal to noise ratio, for example, about 6.0dB or better. The secondary data coils 266, 268 may have fewer turnsthan the power transmitting 234 and receiving coils 232.

The secondary data coils 266, 268 may be orthogonal to the power coils232, 234, as illustrated in FIG. 14. For example, the magnetic flux fromthe power transmitting coils 232, 234 may be orthogonal to a first datacoil 266, so that it does not induce a signal in the first data coil266. A second data coil 268 may be wrapped as shown in FIG. 14 such thatmagnetic flux from the power transmitters does not pass through it, butmagnetic flux from first data coil 266 does. Notably, the configurationdepicted in FIG. 14 is offered for illustrative purposes only and is notmeant to suggest that it is the only configuration that may reduce oreliminate the possibility that a signal will be induced in one or moreof the data coils by the magnetic flux of the power transmitting coils.Other data coil configurations that may minimize the magnetic flux fromthe power transmitter exciting the data coils will occur to those withordinary skill in the art.

Moreover, it is envisioned that the data coils 266, 268 may be wound ona non-magnetic dielectric material in some embodiments. Using a magneticcore for the data coils 266, 268 might result in the data coils' coresbeing saturated by the strong magnetic fields used for powertransmission. Also, the data coils 266, 268 may be configured to operateat a substantially different frequency than the power transmissionfrequency. For example, if the power is transmitted at about 100.0 kHzin a certain embodiment, then the data may be transmitted at a frequencyof about 1.0 MHz or higher. In such an embodiment, high pass filters onthe data coils 266, 268 may prevent the about 100.0 kHz signal fromcorrupting the data signal. In still other embodiments, the data coils266, 268 may simply be located away from the power coils 232, 234 tominimize any interference from the power transmission. It is furtherenvisioned that some embodiments may use any combination of thesemethods to mitigate or eliminate adverse effects on the data coils 266,268 from the power transmission of the power coils 232, 234.

FIGS. 15A1-16C2 are diagrams of tools 305, 310 in a bottom hole assembly100 of a drill string 12 that are coupled via embodiments of a wirelessdrilling and mining (“D&M”) extender 301. Advantageously, a wireless D&Mextender 301 provides for replacement of a physical pin connection ofthe conventional art with a stationary tuned-inductive coupler mechanismconfigured to pass power and data communication transmissions from toolto tool. As is understood by one of ordinary skill in the art ofinductive coupling or magnetic coupling, a change in current flowthrough one coil may induce a voltage across an adjacent coil throughelectromagnetic induction.

The amount of inductive coupling between two conductors is measured bytheir mutual inductance. Inductive coupling may be leveraged in thismanner between two wires, however one of ordinary skill in the art willrecognize that the coupling between two wires can be increased bywinding them into coils and placing them close together on a commonaxis, so the magnetic field of one coil passes through an and in and methe other coil.

It is envisioned that embodiments of a wireless D&M extender may includeseparate stationary coils or wires for power and data communicationstransmission. Power exchanged between the stationary coils would have afrequency in hundreds of kiloHertz (kHz) while data transmissionsbetween the stationary coils would likely occur in the megahertz (MHz)range as understood by one of ordinary skill in the art.

As described above, smaller stationary coils, such as coils 266, 268 ofFIG. 14 would be used in conjunction with larger coils 232, 234. Thesmaller stationary coils 266, 268 may transmit data communications whilethe stationary larger coils 232, 234 would transmit power signals. Asunderstood by one of ordinary skill the art, the larger coils 232, 234and the smaller coils 266, 268 may share a common ferrite core 235 suchthat one ferrite core 235 has two sets of coils: one coil having ahigher number of windings for power transfer while a second coil has alower number of windings for data transfer.

Returning to FIGS. 15A1-15C2, FIG. 15A1 depicts a stationary/fixed“mandrel to mandrel” embodiment of a wireless D&M extender 301A forstationary tools that do not move, translate, or rotate relative to eachother. In the FIG. 15A1 embodiment, tool 310A includes a mandrel typecoil 311A that is communicatively coupled to a mandrel type coil 306A oftool 305A via a tuned-inductive coupler arrangement. As explained above,power and/or data communications may be transmitted between tools 305A,310A via inductive coupling between coils 306A, 311A for tool 305, 310that are generally fixed or do not move relative to each other.

Advantageously, although stationary coils 306A, 311A may be juxtaposedsuch that a change in current flow in one coil induces a voltage in theother, the coils 306A, 311A are not required to be mechanically coupledor rigidly aligned when the tools 305, 311 are connected together. Thatis, it is envisioned that in a wireless D&M extender, a gap (not easilyseen in FIG. 15A1 but see FIG. 15A2) may exist between coils 306A and311A even though the tools 305, 310 may have a fixed coupling 323 (seeFIG. 15A2), such as screw threads, rivets, or welds for engaging eachother. As such, mechanical wear, misalignment, and/or vibration in thephysical connections between various tools 305A, 310A of a given BHA maynot adversely affect or otherwise cause the failure of thecommunications bus.

FIG. 15A2 depicts an enlarged view of the stationary “mandrel tomandrel” embodiment of a wireless D&M extender 301A. The fixed coupling323 between the two tools 310A and 305A, in which the first tool 310Amay include a drill collar pin connection while the second tool 305A mayinclude a drill collar box connection, is illustrated in further detail.The coupling 323 between tools 305, 310 may include screw threads and/orother secure mechanical fasteners, like bolts, screws, rivets, welds,and other similar fasteners as understood by one of ordinary skill theart. The coupling 323 is designed to provide a rigid and non-movingconnection between the tools 305, 310.

Meanwhile, the stationary coils 311A, 306A may be coupled to respectiveand extenders 1605. The extenders 1605 may be coupled to respectivepressure housings (not illustrated) which enclose or shield electronicsthat generate at least one of communication signals and power signals.The extender 1605 may be made from a metal that is non-magnetic, such asstainless steel. A gap distance g may exist between the two coils 311C,306C. The gap distance g is usually not greater than twice the diameterT of a respective ferrite core 235.

In the FIG. 15B embodiment, tool 310B includes an annular type coil 311Bthat is communicatively coupled to a mandrel type coil 306B of tool 305Bvia a tuned-inductive coupler arrangement. As explained above, powerand/or data communications may be transmitted between tools 305B, 310Bvia inductive coupling between coils 306B, 311B. Advantageously,although coils 306B, 311B are positioned juxtaposed such that a changein current flow in one coil induces a voltage in the other, the coils306B, 311B are not required to be mechanically coupled or rigidlyaligned.

That is, it is envisioned that in a wireless D&M extender, a gap 315 mayexist between coils 306B and 311B. As such, mechanical wear,misalignment, and/or vibration in the physical connections betweenvarious tools 305B, 310B of a given BHA may not adversely affect orotherwise cause the failure of the communications bus. The stationaryannular type coil 311B is described in more detail above in connectionwith FIGS. 5A-5B.

In the FIG. 15C1 embodiment, tool 310C includes a stationary annulartype coil 311C that is communicatively coupled to a stationary annulartype coil 306C of tool 305C via a tuned-inductive coupler arrangement.As explained above, power and/or data communications may be transmittedbetween tools 305C, 310C via inductive coupling between coils 306C,311C. Advantageously, although coils 306C, 311C are juxtaposed such thata change in current flow in one coil induces a voltage in the other, thecoils 306C, 311C are not required to be mechanically coupled or rigidlyaligned.

That is, it is envisioned that in a wireless D&M extender, a gap (noteasily seen in FIG. 15C1 but see FIG. 15C2) may exist between coils 306Cand 311C. As such, mechanical wear, misalignment, and/or vibration inthe physical connections between various tools 305C, 310C of a given BHAmay not adversely affect or otherwise cause the failure of thecommunications bus.

FIG. 15C2 provides an enlarged view of the stationary annular type coil311C that is communicatively coupled to a stationary annular type coil306C of tool 305C in FIG. 15C1. The ferrite cores 235 of thisarrangement may have a hollow cylindrical shape. As noted previously, agap distance g may exist between the two coils 311C, 306C. The gapdistance g is usually not greater than twice the thickness T of arespective ferrite core 235.

FIG. 16A illustrates a wireless power distribution scheme 402 betweentwo stationary tools such as a MWD 130 and a LWD 120 that leveragesalternating current (“AC”) to transmit power in a BHA 100. In the FIG.16A illustration, MWD tool 130 is the power source for LWD tool 120. Thepower is generated in MWD tool 130 via a turbine 425, although otherpower sources such as, but not limited to, batteries are envisioned. Thepower generated by turbine 425 is supplied through AC/DC module 420 andswitching amp 415 to source resonators 410 and 430. The sourceresonators 410, 430 may be leveraged to wirelessly transmit power and/ordata communications to a receiving device resonator in a juxtaposedtool, such as device resonator 440 in LWD tool 120. The transmissionsare then used within LWD tool 120 and relayed to subsequent tools in thegiven BHA via source resonator 450.

FIG. 16B illustrates a wireless power distribution scheme 402 betweentwo stationary tools like a MWD 130 and LWD 120 that leveragesalternating current (“AC”) and direct current (“DC”) to transmit powerin a BHA 100. The wireless power distribution scheme 402 largely mirrorsthat of scheme 402 in FIG. 16A with the exception that the ACtransmission is converted within LWD tool 120 to DC and then back to ACfor subsequent transmission to other tools via source resonator 450.

Although a few embodiments have been described in detail above, thoseskilled in the art will readily appreciate that many modifications arepossible in the embodiments without materially departing from thisdisclosure. Accordingly, such modifications are intended to be includedwithin the scope of this disclosure as defined in the following claims.In the claims, means-plus-function clauses are intended to cover thestructures described herein as performing the recited function and notonly structural equivalents, but also equivalent structures. Thus,although a nail and a screw may not be structural equivalents in that anail employs a cylindrical surface to secure wooden parts together,whereas a screw employs a helical surface, in the environment offastening wooden parts, a nail and a screw may be equivalent structures.It is the express intention of the applicant not to invoke 35 U.S.C.§112, sixth paragraph for any limitations of any of the claims herein,except for those in which the claim expressly uses the words ‘means for’together with an associated function.

What is claimed is:
 1. A drilling and mining (“D&M”) extender device forcommunicatively coupling two stationary tools in a bottom hole assemblyof a drill string, the extender device comprising: a first stationarycoil associated with a first tool; and a second stationary coilassociated with a second tool; wherein electrical transmissions betweenthe first and second tools are transmitted wirelessly between the firstand second stationary coils via inductive coupling between the coils;the first stationary coil positioned proximate to the second stationarycoil; the coils are inductively coupled such that: k=M/√{square rootover (L₁L₂)}≦0.9, wherein k is the coupling coefficient of the coils, Mis the mutual inductance between the coils, and L₁ and L₂ are theself-inductances of the respective coils; each coil is resonantly tunedwith a capacitor such that: f₁≈f₂, wherein$f_{1} = \frac{1}{2\; \pi \sqrt{L_{1}C_{1}}}$ and$f_{2} = \frac{1}{2\; \pi \sqrt{L_{2}C_{2}}}$ and f₁ and f₂ are thefrequencies in Hertz of the respective coils, L₁ and L₂ are theself-inductances of the respective coils, and C₁ and C₂ are capacitancesof tuning capacitors associated with the respective coils; and the coilshave an associated figure of merit, U, such that: U=k√{square root over(Q₁Q₂)}≧3, wherein $Q_{1} = \frac{2\; \pi \; f_{1}L_{1}}{R_{1}}$and $Q_{2} = \frac{2\; \pi \; f_{2}L_{2}}{R_{2}}$ and Q1 and Q2 arethe quality factors associated with the respective coils, f₁ and f₂ arethe frequencies in Hertz of the respective coils, L₁ and L₂ are theself-inductances of the respective coils, and R₁ and R₂ are theresistances of the respective coils.
 2. The drilling and mining extenderdevice of claim 1, wherein the first tool has an impedance as a source,R_(S) wherein the impedance is governed by the equation:R _(S) ≈R ₁√{square root over (1+k ² Q ₁ Q ₂)}, wherein R₁ is the seriesresistance of the first coil, k is the coupling coefficient of the pairof coils, Q₁ is the quality factor associated with the first coil and Q₂is the quality factor associated with the second coil.
 3. The drillingand mining extender device of claim 2, further comprising approximatelymatching an impedance of the second tool with an impedance of the sourceby setting:R _(L) ≈R ₂√{square root over (1+k ² Q ₁ Q ₂)}, wherein R₂ is the seriesresistance of the second coil, k is the coupling coefficient of the pairof coils, Q₁ is the quality factor associated with primary coil and Q₂is the quality factor associated with the second coil.
 4. The drillingand mining extender device of claim 1, wherein one or more of theelectrical transmissions are selected from the group of powertransmissions and data communication transmissions.
 5. The drilling andmining extender device of claim 1, wherein the first coil is of amandrel type and the second coil is of a annular type.
 6. The drillingand mining extender device of claim 1, wherein the first coil is of amandrel type and the second coil is of a mandrel type.
 7. The drillingand mining extender device of claim 1, wherein the first coil is of anannular type and the second coil is of an annular type.
 8. The drillingand mining extender device of claim 1, wherein the first tool and secondtool mate together using a fixed and non-movable coupling.
 9. Thedrilling and mining extender device of claim 8, wherein the fixed andnon-movable coupling comprises a mechanical fastener.
 10. The drillingand mining extender device of claim 9, wherein the fixed and non-movablecoupling comprises at least one of screw threads, rivets, and welds. 11.A drilling and mining (“D&M”) extender device for communicativelycoupling two stationary tools in a bottom hole assembly of a drillstring, the extender device comprising: a first stationary coilassociated with a first tool; and a second stationary coil associatedwith a second tool; wherein electrical transmissions between the firstand second tools are transmitted wirelessly between the first and secondstationary coils via inductive coupling between the coils; the firststationary coil positioned proximate to the second stationary coil, thefirst tool and second tool mate together using a fixed and non-movablecoupling.
 12. The drilling and mining extender device of claim 11,wherein the fixed and non-movable coupling comprises at least one ofscrew threads, rivets, and welds.
 13. The drilling and mining extenderdevice of claim 11, wherein the coils are inductively coupled such that:k=M/√{square root over (L₁L₂)}≦0.9, wherein k is the couplingcoefficient of the coils, M is the mutual inductance between the coils,and L₁ and L₂ are the self-inductances of the respective coils; eachcoil is resonantly tuned with a capacitor such that: f₁≈f₂, wherein$f_{1} = \frac{1}{2\; \pi \sqrt{L_{1}C_{1}}}$ and$f_{2} = \frac{1}{2\; \pi \sqrt{L_{2}C_{2}}}$ and f₁ and f₂ are thefrequencies in Hertz of the respective coils, L₁ and L₂ are theself-inductances of the respective coils, and C₁ and C₂ are capacitancesof tuning capacitors associated with the respective coils; and the coilshave an associated figure of merit, U, such that: U=k√{square root over(Q₁Q₂)}≧3, wherein $Q_{1} = \frac{2\; \pi \; f_{1}L_{1}}{R_{1}}$and $Q_{2} = \frac{2\; \pi \; f_{2}L_{2}}{R_{2}}$ and Q1 and Q2 arethe quality factors associated with the respective coils, f₁ and f₂ arethe frequencies in Hertz of the respective coils, L₁ and L₂ are theself-inductances of the respective coils, and R₁ and R₂ are theresistances of the respective coils.
 14. The drilling and miningextender device of claim 11, wherein one or more of the electricaltransmissions are selected from the group of power transmissions anddata communication transmissions.
 15. The drilling and mining extenderdevice of claim 11, wherein the first coil is of a mandrel type and thesecond coil is of a annular type.
 16. The drilling and mining extenderdevice of claim 11, wherein the first coil is of a mandrel type and thesecond coil is of a mandrel type.
 17. The drilling and mining extenderdevice of claim 11, wherein the first coil is of an annular type and thesecond coil is of an annular type.
 18. A wireless coupling for drillingcomprising: a first stationary coil attached to a first drillingstructure; and a second stationary coil attached to a second drillingstructure; wherein electrical transmissions between the first and secondcoils are transmitted wirelessly via inductive coupling between thecoils; the first stationary coil positioned proximate to the secondstationary coil, the first drilling structure and second drillingstructure being held in position with a fixed and non-movable fasteningmechanism.
 19. The wireless coupling of claim 18, wherein the fixed andnon-movable fastening mechanism comprises at least one of screw threads,rivets, and welds.
 20. The wireless coupling of claim 19, wherein thecoils are inductively coupled such that: k=M/√{square root over(L₁L₂)}≦0.9, wherein k is the coupling coefficient of the coils, M isthe mutual inductance between the coils, and L₁ and L₂ are theself-inductances of the respective coils; each coil is resonantly tunedwith a capacitor such that: f₁≈f₂, wherein$f_{1} = \frac{1}{2\; \pi \sqrt{L_{1}C_{1}}}$ and$f_{2} = \frac{1}{2\; \pi \sqrt{L_{2}C_{2}}}$ and f₁ and f₂ are thefrequencies in Hertz of the respective coils, L₁ and L₂ are theself-inductances of the respective coils, and C₁ and C₂ are capacitancesof tuning capacitors associated with the respective coils; and the coilshave an associated figure of merit, U, such that: U=k√{square root over(Q₁Q₂)}≧3, wherein $Q_{1} = \frac{2\; \pi \; f_{1}L_{1}}{R_{1}}$and $Q_{2} = \frac{2\; \pi \; f_{2}L_{2}}{R_{2}}$ and Q1 and Q2 arethe quality factors associated with the respective coils, f₁ and f₂ arethe frequencies in Hertz of the respective coils, L₁ and L₂ are theself-inductances of the respective coils, and R₁ and R₂ are theresistances of the respective coils.